Jet lag

The weather is great, that meeting or your holiday can begin - but you feel exhausted. What you have is "jet lag", the well-known phenomenon that troubles many long-haul passengers during their first few days in a far-off country. For while the sun has long been shining, your body thinks it's still at home, where it is now the middle of the night or early morning.

Causes

People normally live in a 24-hour rhythm. While we sleep, the heart and breathing rates slow, the blood presssure drops, the muscles relax and the mental and psychomotoric efficiency declines significantly.

A rapid change to another location in another time zone disturbs phases in the human daily rhythm. It interrupts not only people's usual cycles of sleeping and being awake, but also the regular course of a great number of disparate bodily functions that operate in a 24-hour rhythm.

Effects

Tiredness and slowed reactions combined with memory and concentration problems are the most frequent results. People can also feel exhausted and suffer headaches and a sense of nausea due to the interruption of their normal sleeping time.

Jet lag effects are more marked after an Eastbound flight than a Westbound one. The reason for this difference is that the human "inner clock" tends towards a rhythm of more than 24 hours. So if you fly from East to West (such as from Germany to the USA), the day is longer - which tends to suit the biological rhythm. The human body adjusts to the new time zone about 20 percent faster than after an Eastbound flight (such as from Germany to Thailand), because flying East means it "loses" several hours.